1. Field of the Invention
The present invention generally relates to a method for reconstructing a three dimensional (3D) model, in particular, to a method for reconstructing a 3D model by cutting a voxel layer by layer to approach a silhouette image of an object.
2. Description of Related Art
Common algorithms of reconstructing a 3D model of an object can be approximately classified into active and passive types. In conventional art, for the active reconstruction manner, a pattern is projected onto the object by light, and through reflection of the light rays, 3D geometric information of the object is calculated by variation of the light pattern in the image or a triangulation method. However, if the material (for example, glass) of the object cannot effectively reflect the pattern, the active method fails. For another passive visual reconstruction technology reconstructing the 3D model of the object purely by using camera to capture the images, the problem is prevented, and the cost of the whole image capture device is saved.
Recently, in computer visual field, many researchers get involved in the research works. For one reconstruction technology using object silhouette information, the 3D region of the object is represented by using a view volume formed by the silhouette of the object and a center of projection of the camera. If intersection operation is performed on the view volumes with different angles, a 3D model approaching the object can be obtained.
Practically, when using the technology, one method is that the 3D space is cut into voxels without intersections. For example, the 3D space is cut into a plurality of voxels, and through the projections of the voxels on the silhouette images, it is determined whether the voxels and the space occupied by the practical object have the intersections. In this manner, the voxels having the intersections with the space occupied by the practical object are reserved, so as to obtain a 3D model approaching the shape of the object. Therefore, the more the number of the cut layers of the voxel is, the higher the accuracy of the obtained 3D model is.
However, as resolution of the image sensing element is improved, no matter for digital camera or photographic mobile phone, shot images all easily exceed three million pixels. Correspondingly, when the 3D model is reconstructed by using the high pixel images, in order to obtain the 3D model with high accuracy, the quantity of the voxels required to be stored is quite large, so the space required to store the voxels will be quickly increased with the number of the cut layers. Therefore, a large amount of memories are required for storage and calculation.